[turbofan] Push TruncateFloat64ToInt32 into phis.

src/compiler/machine-operator-reducer.cc

Index: src/compiler/machine-operator-reducer.cc
diff --git a/src/compiler/machine-operator-reducer.cc b/src/compiler/machine-operator-reducer.cc
index 53b1d8006ab2ce9d4e6970da7d0dd9cf5b216fbf..bb1596f58bd93e74e8467555f6053cf2988dca49 100644
--- a/src/compiler/machine-operator-reducer.cc
+++ b/src/compiler/machine-operator-reducer.cc
@@ -523,12 +523,8 @@ Reduction MachineOperatorReducer::Reduce(Node* node) {
       if (m.HasValue()) return ReplaceInt64(static_cast<uint64_t>(m.Value()));
       break;
     }
-    case IrOpcode::kTruncateFloat64ToInt32: {
-      Float64Matcher m(node->InputAt(0));
-      if (m.HasValue()) return ReplaceInt32(DoubleToInt32(m.Value()));
-      if (m.IsChangeInt32ToFloat64()) return Replace(m.node()->InputAt(0));
-      break;
-    }
+    case IrOpcode::kTruncateFloat64ToInt32:
+      return ReduceTruncateFloat64ToInt32(node);
     case IrOpcode::kTruncateInt64ToInt32: {
       Int64Matcher m(node->InputAt(0));
       if (m.HasValue()) return ReplaceInt32(static_cast<int32_t>(m.Value()));
@@ -692,6 +688,36 @@ Reduction MachineOperatorReducer::ReduceUint32Mod(Node* node) {
 }
 
 
+Reduction MachineOperatorReducer::ReduceTruncateFloat64ToInt32(Node* node) {
+  Float64Matcher m(node->InputAt(0));
+  if (m.HasValue()) return ReplaceInt32(DoubleToInt32(m.Value()));
+  if (m.IsChangeInt32ToFloat64()) return Replace(m.node()->InputAt(0));
+  if (m.IsPhi()) {
+    Node* const phi = m.node();
+    DCHECK_EQ(kRepFloat64, RepresentationOf(OpParameter<MachineType>(phi)));
+    if (phi->OwnedBy(node)) {
+      // TruncateFloat64ToInt32(Phi[Float64](x1,...,xn))
+      //   => Phi[Int32](TruncateFloat64ToInt32(x1),
+      //                 ...,
+      //                 TruncateFloat64ToInt32(xn))
+      const int value_input_count = phi->InputCount() - 1;
+      for (int i = 0; i < value_input_count; ++i) {
+        Node* input = graph()->NewNode(machine()->TruncateFloat64ToInt32(),
+                                       phi->InputAt(i));
+        // TODO(bmeurer): Reschedule input for reduction once we have Revisit()
+        // instead of recursing into ReduceTruncateFloat64ToInt32() here.
+        Reduction reduction = ReduceTruncateFloat64ToInt32(input);
+        if (reduction.Changed()) input = reduction.replacement();
+        phi->ReplaceInput(i, input);
+      }
+      phi->set_op(common()->Phi(kMachInt32, value_input_count));
+      return Replace(phi);
+    }
+  }
+  return NoChange();
+}
+
+
 Reduction MachineOperatorReducer::ReduceStore(Node* node) {
   MachineType const rep =
       RepresentationOf(StoreRepresentationOf(node->op()).machine_type());